Primary cells having charge transfer complexes, such as iodine-containing material are generally well known. High energy density batteries utilizing a lithium anode and cathode or organic material such as polycyclic aromatic compounds, organic polymers, heterocyclic nitrogen containing compounds and the like and a halide such as iodine have been disclosed. U.S. Pat. No. 3,660,163. Additionally, cathode compositions comprising a mixture of iodine and poly-2-vinylpyridine. nI.sub.2 or poly-2- vinylquinoline. nI.sub.2, wherein n= 2-15 have been taught; U.S. Pat. No. 3,674,562, incorporated herein by reference. Cathode material of this latter type is typically a pliable, plastic-like solid having a flowable viscosity.
Lithium halide batteries of the present invention are typically used with implantable prosthetics such as cardiac pacemakers. For such application, it is necessary that the battery be physically small and highly reliable. In attaining high reliability, both the design of and the methods for manufacturing the battery are of great importance.
Of the many problems that can arise from poor design or manufacturing processes of lithium halide cells, obtaining satisfactory sealing of the depolarizer within the container is one of the most critical. In many processes, it is difficult, if not impossible, to determine whether a battery will leak until it has been completely assembled with its heremetic seal and tested. Failure to achieve a leak-proof seal requires discarding the battery with little or no salvage. Moreover, it is often times difficult to determine whether a leak-proof seal has been achieved until the battery has been placed in service.
To overcome this and many of the problems that often arise in the manufacture of lithium-halide batteries, a method is disclosed, U.S. patent application Ser. No. 666,161, filed Mar. 12, 1975, now U.S. Pat. No. 4,010,043, in which the cell comprises a lithium receiving vessel which functions as the anode of the battery and as the container of the cathode material. The cathode material is poured into the vessel and a cathode current collector is positioned within the cathode material and the lead is positioned so as to be at least partially embedded within the lithium. The vessel is thereafter cooled to a temperature sufficient to solidify the cathode material. Sealing of the vessel is achieved by positioning a lithium cap on the solidified material and cold welding or diffusion bonding the cap under pressure to the receiving vessel to form a lithium anode encassing member.
The present invention is an important improvement on the method taught and disclosed therein.
It is an object of the present invention to provide a lithium anode cell having one defined end and a flat lithium seal on the other to permit the fabrication of cells of varying lengths from one set of vessel forming molds. It is a further object of the present invention to provide a cell and a method wherein the cathode lead is embedded within the lithium encasing vessel to maximize any possible path for depolarizer leakage. It is also an object of the present invention to provide a method and means wherein the cathode current collector assembly is positioned within the lithium receiving vessel so as to be electrically isolated from the lithium encasement vessel.